Removal techniques, e.g., etching and cleaning, are universally practiced on semiconductor materials, metal materials, and/or dielectric materials in the production of electronic devices and/or materials. Because of the importance of these procedures, extensive research has been expended in improving established techniques and developing novel approaches. Through this research, processing times have been significantly diminished, and the quality of these processes has been substantially improved.
As semiconductor wafer processing machines move toward more automation, cassettes are used to move the wafers from one machine to another. The cassettes in many cases, are made of soft plastic to avoid damage to the wafers. Such cassettes, however, are subject to warping and deformation in use and are not dimensionally stable. Sometimes wafers are broken or otherwise removed from the group of wafers in the cassette, thereby creating a blank space in the cassette. Valuable processing time is thereby wasted.
Semiconductor wafer processing requires many steps in many processing chambers. Isolation means must be provided between chambers and means for moving wafers must be provided compatible with the isolation. All this must be provided in a way which generates a minimum of particulates which might contaminate the wafer. Generally, isolation is provided by valves and wafer movement is handled by an independent mechanism.
U.S. Pat. Nos. 4,433,951 and 4,483,654 to Koch et al disclose a transfer mechanism in an isolation chamber. Separate valves are required on either side of the isolation chamber. The transfer mechanism within the isolation chamber is complex and prone to particulate generation problems.
U.S. Pat. No. 4,533,069 to Purser discloses a wafer handling arm having four trapezoidally-shaped sides. The side arms extend sideways as the arm is shortened, thereby requiring a large opening in which to operate the arm.
U.S. Pat. No. 3,921,788 to Roberson, Jr. et al discloses a wafer handling mechanism on a slide mechanism. The slide mechanism is inherently present in the work area and subject to generation of particulates.
In prior art wafer processing machines the holding of the semiconductor wafer was often a simple device since the wafers were loaded by hand. As semiconductor processing moved into more sophisticated sequential automated processing, wafer handling means had to be devised which would pass a wafer to a wafer holding device. Where it is necessary to temperature regulate the wafer during processing, various means can be employed. Heat transfer problems arise where a temperature controlled chuck is used in a vacuum to regulate the temperature of a wafer. One of the most reliable heat transfer means is to provide gas at the back of the wafer at a pressure between 3 and 20 Torr (depending on the process) and allow this gas to equilibrate the temperature of the chuck and wafer through conduction and/or convection as shown in U.S. Pat. Nos. 4,512,391; 4,514,636; and 4,565,601. In order to efficiently control the temperature of the wafer it is necessary that the wafer holding means clamp the wafer firmly to the temperature controlled chuck. The wafer clamping means and handling means must interact in a reliable manner.